UCLA

This thesis establishes a fiber-based dip probe method for in situ time correlated single photon counting (TCSPC), enabling real time photoluminescent lifetime monitoring in dynamic chemical system without disrupting the native sample environment. Unlike intensity-based measurements, which depend on experimental conditions, luminescent lifetimes are ratiometric, intrinsic to the excited state, and provide direct insight to sample photophysical properties that are directly linked to local environment changes. By integrating a fiber optic probe with TCSPC, lifetimes can be directly monitored in experimental chemistry environments that have otherwise been inaccessible, extending the reach of photoluminescent lifetime spectroscopy beyond current, conventional tabletop, cuvette based optical setups. In addition to in situ monitoring, the dip probe method allows for rapid sequential lifetime measurements across multiple samples with minimal maintenance of the system, allowing for more automated, high-throughput measurements of luminescent properties. These methods are demonstrated across four systems: sequential lifetime measurements of synthetic dyes, Rhodamine 6G and 3,3′-bis(2-sulfopropyl)-5,5′,6,6′-tetrachloro-1,1′-dioctylbenzimidacarbocyanine (C8S3) monomer, and dynamic studies of ultrasmall Mercury Telluride (HgTe) quantum dot synthesis, as well as J-aggregation of both C8S3 ribbons and double-walled nanotubes (DWNTs). These chemical systems establish the dip probe as a versatile platform for probing excited-state dynamics in situ, while also providing a practical, high-throughput route for consecutive lifetime measurements.